Extreme pressure lubrication additive

ABSTRACT

The reaction product of an alkyl tallate, sulfur and dialkyl phosphonate is found to function as an extreme pressure additive in lubricating compositions.

United States Patent Hotten Aug. 12, 1975 1 EXTREME PRESSURE LUBRICATION 3,206,401 9/1965 OHalloran 252/466 ADDITWE 3,415,767 12/1968 Kelly 260 975 3,423,389 1/1969 Wheelus 260/975 [75] In ent r: ru tt n Ca if. 3,455,830 7/1969 Lawrence 252/466 3,455,844 7 1969 B 252 46.6 [73] Assgnw Research compmy San 3.583915 6/1971 252/466 Franc1sco, Calrf.

[22] Filed: 1972 Primary Examiner-Me'lvyn I. Marquis [21] Appl. No.: 297,575 Assistant Examiner-William E. Parker Attorney, Agent, or Firm-G. F. Magdeburger; C. J. T k' M. D. N l 52 US. Cl. 260/975; 252/466; 252/484; 8

260/399; 260/403; 260/405.5 [5 Int. [58] Field of Search 260/975, 403, 399, 405.5, 1

260/410; 252/484, 46.6 The reaction product of an alkyl tallate, sulfur and dialkyl phosphonate is found to function as an extreme [56] References Cited pressure additive in lubricating compositions.

UNITED STATES PATENTS N; D 3,l89,628 6/1965 Knight 252/403 svcla'ms 'awmgs EXTREME PRESSURE LUBRICATION ADDITIVE BACKGROUND OF THE INVENTION Field of the Invention The control of friction and wear under high load conditions requires boundary lubrication. Boundary lubrication depends on properties of the lubricant other than its viscosity such as the tendency toward the formation of films on metallic surfaces. While the formation of such films is thermodynamically favored, the thickness of the film ranges from a few hundredths of a microinch for single molecular layers of adsorbed gases to several dozen microinches for thick films from oils with extreme pressure (EP) additives. A problem in the lubrication art is to provide a boundary film with the proper chemical and physical characteristics to control friction and/or wear under high load conditions, and the correct chemical properties to avoid detrimental damage to the surface and other disadvantageous effects such as toxicity, oxidation catalysis and sludge deposition.

Lead naphthenates have often been used in conjunction with sulfurized compounds to produce lubricating compositions with extreme pressure and anti-wear properties. However, lead naphthenate compositions contain all of the disadvantages heretofore discussed. The present invention provides non-lead containing lubricants which are capable of exhibiting excellent EP properties.

SUMMARY OF THE INVENTION Extreme pressure, anti-friction and anti-wear addi tives for lubricating oils are prepared by sulfurizing or phosphosulfurizing unsaturated fatty acid esters of a Cut-C fatty acid and a C C- alkanol or alkenol by reaction with a C C dialkyl phosphonate which is a diester of phosphonic acid,

I OH

having the general formula I OR wherein R and R are C -C alkyl groups, The fatty acid ester can be the tallate obtained from the esterification of derosinified tall oil. The additive when present at only the 0.2 weight percent level is found to im' part anti-wear properties, and at high concentrations, both extreme pressure and antiwear properties are imparted to the lubricating oil. Timken test maximum load values reach 60 pounds at only about 8 weight percent sulfur in the additive.

DETAILED DESCRIPTION OF THE INVENTION This invention provides a novel class of oiliness agents which are prepared by reacting an unsaturated fatty acid ester of a C -C fatty acid and a C,C alkanol or alkenol with sulfur and a C -C dialkyl phosphonate.

Examples of the fatty acid include unsaturated monoethenoid acids such as oleic acid, C H COOH, palmitoleic acid, C H COOH, petroselinic acid, C H COOH, erucic acid, C- H COOI-I, gadoleic acid, C H COOH, vaccenic acid, C H COOH, and other naturally occuring and synthetic acids of the general formula: C,,H ,COOH; and unsaturated polyethenoid acids such as linoleic acid, C H COOH. Also included when admixed with unsaturated acids or alkenols are saturated acids such as n-undecanoic, C I-I COOH, lauric acid, C H COOI-I, myristic acid, C, -,H COOH, palmitic acid, C, H COOH, stearic acid, C H COOH, and other naturally occuring and synthetic acids of the formula: C,,H COOH. Branched-chain fatty acids are also included, as well as substituted acids such as ricinoleic acid, C H OH- COOI-I.

Examples of the alcohols which find use within the scope of the present invention are methyl alcohol, propyl alcohol, butyl alcohol, hexanol, octanol, undecanol, tetradecanol, etc. Monoethenoid and polyethenoid oils are also included, such as l-hydroxy-3-hexene, 2- hydroxy-S, 7-dodecadiene, 1-hydroxy-4,7- pentadecadiene, 2-hydroxy-10-dodecene, etc. The alcohol can be straight chain or branched chain or partially branched and partially straight-chain. Substituted alcohols are also included, such as the 1,2-glycols, 1,3- glycols, etc. as well as the polyols.

Although saturated alcohols or fatty acids may be used inpart to form the unsaturated ester, sufficient unsaturated reactants should be used to form an ester containing an average of about 12 double bonds per ester molecule.

A particularly preferred embodiment of this invention is the product of the reaction of oleic or linoleic acid with a C -C alcohol, such as undecyl alcohol. One mole of this ester product is then sulfurized with one or more moles of sulfur, depending upon the average number of double bonds present in the ester. It is an essential element of the invention that either the alcohol or the fatty acid be unsaturated. This is necessary for effective sulfurization. Although the usefulness of these materials as lubricating additives is independent of any particular supposition about the structure of the sulfurized product, it is believed that the sulfurization step introduces sulfur by forming linkages with (S),, between ethylenic double bond positions. Thus, it is believed that either the alcoholic or acidic portion of the ester molecule must be unsaturated to form effective linkages with other molecules.

The esters within the scope of the present invention are illustrated by isopropyl oleate, ethyl linoleate, pentadecyl oleate, eicosyl linoleate, decenyl stearate, eicosenyl laurate, propy] linoleate, pentadecenyl linoleate, undecyl ricinoleate, pentadecyl tallate, etc.

Tall oil is a by-product of the sulfate process for the manufacture of wood pulp. It consists of about 50 percent resin acids. The resin obtained from various species of pine is called rosin, which is chiefly abietic acid, C H O- The remaining 50 percent of tall oil consists of unsaturated fatty acids, chiefly oleic and linoleic acids. Thus derosinified tall oil is a convenient source of these unsaturated acids. Rosin is a source of undesirable auxiliary properties of lube oil additives when it is present in high percentage in tall oil prior to neutralization and/or sulfurization. Derosinified tall oil is commercially available. For use in embodiments of the present invention, the derosinified tall oil should contain less than 5 percent of rosin.

Method of Preparation In a preferred embodiment of the invention, derosini fied tall oil is reacted with an alkyl alcohol and sulfurized to the extent of 5-30 percent of sulfur by weight. Concurrently, or sequentially, the sulfurized ester is reacted with dialkyl phosphonate in the mole ratio of ester to sulfur to phosphonate of l:l-2:0. l0.5 at 150l 80C for about 220 hours.

The ester substrate may be prepared by any of the well-known methods. Typically, as described in the following example, the ester is prepared by heating an unsaturated carboxylic acid, such as oleic acid, with a slight excess of an alcohol, such as tridecanol with or without a catalyst, such as sulfonated polystyrene. The product should contain one or more double bonds per molecule to provide suitable capacity for reaction with sulfur and dialkyl phosphonate.

The unsaturated ester is preferably heated with sufficient sulfur and dialkyl phosphonate to convert it to a mixture of mainly thioethers, dithioethers and trithioethers, with small portions of thiophosphonates. The reaction temperature should be about l50l 80C and the time in inverse order to temperature, from 2-20 hours. A nitrogen sparge is useful for removing small quantities of hydrogen sulfide that form as a byproduct. Otherwise, no further treatment is necessary.

EXAMPLE 1 Into a 2 liter flask is charged 880 g. (about 2 mols) of the alkyl tallate ofa C -C alkanol, 90 g. (about 2.8 mols) of sulfur, and 58 g. (about 0.3 mols) of dibutyl phosphonate, (C H O) PHO. The mixture is heated and stirred under nitrogen at 170 i 7C for 6 hours. The product is used directly. Percent phosphorus, 0.88 percent.

EXAMPLE 2 620 grams (about 1 mole) of the unsaturated ester, alkenyl stearate, produced from the reaction of oleyol with stearic acid, is sulfurized with 45 -g. (about 1.4 mols) of sulfur by heatingand stirring the mixture under nitrogen at about 180C for several hours. The product is then reacted with dihexadecyl phosphonate (about 0.5 mole) for about 4 hours at about 150175C.

EXAMPLE 3 An alkyl tallate of a C -C alkanol, 880 g., having an average of 1.4 double bonds per ester molecule is contacted with 90 g. ofsulfur and 58 g (about 0.3 mols) dibutyl phosphonate in a 2-liter flask for about 6 hours at 160 i 5C under a nitrogen sparge. The product is a dark brown oil whose NMR analysis shows strong ester and dithioether resonances but very weak olefin (about 92% reduction in olefin over unreacted ester). The sulfur and phosphorous content of the product are 8.0 and 0.43 weight percent respectively. At 5 weight percent additive in a 1500 SSU at lOF nonleaded gear oil the Timken extreme pressure test gives 55 lb. and the Copper Strip corrosion test gives la.

EXAMPLE 4 The reaction procedure of Example 3 is carried out with 46 g. (about 0.24 mols) of dibutyl phosphonate yielding a dark brown oily product of similar NMR analysis. Weight percent sulfur and phosphorous are 8.6 and 0.43% respectively. The 5 weight percent nonlead gear oil composition gives Timken test of 65 lb, Copper Strip test of la and 4-Ball wear test of 0.27 mm. Additive Medium Compounds of this invention may be used singly or preferably in combinations of two or more in an oil lubricating viscosity. The lubricating oil can be any relatively inert and stable fluid of lubricating viscosity. Such lubricating fluids generally have viscosities of 3550,000 Saybolt Universal Seconds (SUS) at l0OF. The fluid medium or oil may be derived from either natural or synthetic sources. Included among the natural hydrocarbonaceous oils are paraffin-base, naphthenic base, or mixed base oils. Synthetic oils include polymers of various olefins, generally from two to six carbon atoms, alkylated aromatic hydrocarbons, etc. Non-hydrocarbon oils include polyalkylene oxides, aromatic ethers, silicones, etc. The preferred media are the hydrocarbonaceous media, both natural and synthetic. Preferred are those hydrocarbonaceous oils having viscosity of about lO04,000 SUS and particularly those having viscosity from 2002,000 SUS at 100F. The compounds of this invention may also be used singly, or preferably in combinations of two or more in lubricating greases. Greases comprise oils thickened by gellants or thickeners which are lithium, sodium, and calcium soaps, or synthetic soap-like salts, noncarboxylic salts, polymers, various inorganic com-- pounds, petroleum oils and polysiloxanes.

Lubricating oil or grease will be present at or greater percent by weight of the final lubricant composition. In concentrates, however, the oil may be present as l0-75 percent by weight. These concentrates are diluted with additional oils prior to being placed in service to obtain the requisite concentration.

Other additives may also be present in the composition of this invention. Materials may be added to enhance the EP effect of the additive or provide some other desirable properties to the lubricating medium. These include such additives as rust and corrosion inhibitors, anti-oxidants, oiliness agents, detergents, foam inhibitors, anti-wear agents, viscosity index improvers, pour point depressants, etc. Usually these will be in the range of from about 05 percent by weight, more generally in the range from about 02 percent by weight of the total composition. Typical additional additives found in compositions of the present invention include phenolic and arylamine antioxidants, zinc dihydrocarbyl dithiophosphates, rust inhibitors, such as the metal sulfonates and foam inhibitors such as the polyethyl si loxanes, etc.

LUBRICANT PERFORMANCE The load-carrying capacity of the lubricating fluids of the present invention was tested by means of the Timken extreme pressure tests (ASTM D 2782-71 and the FourBall wear test (ASTM D 2266-67). These tests are widely used for specification purposes and differentime between lubricating fluids having low, medium, and high levels of extreme pressure properties. In the Timken test a steel cup is rotated against a steel block. The rotating speed is 800 rpm and fluid samples are preheated to 38C before starting the test. The test measures the maximum load in pounds at which the rotating cup will not rupture the lubricating film and cause abrasion between the rotatingcupand the stationary block. Thus, the Timken test defines the load carrying capacity of a lubricant as the maximum load or pressure which can be sustained by the lubricant pounds. oils with moderate EP additives will fail at 1,000-1 ,SOOOpounds. and very effective EP additives will permit loadings in excess of 2,000 pounds.

The Copper Strip test (ASTM test method D130) is tive measure of the EP property of the oil composition. As in Table l, mineral oils fail at about 600-900 when used in a given system under specific conditions 5 an important criterion for lack of corrosivity towards without failure of moving bearings or sliding Contact non-ferrous metals. A copper strip is immersed into surfaces as evidenced by seizure or welding. Seizure or 2-4 percent by weight composition of test additives in welding is evidenced by streaks appearing on the suroil at 250F for l to 3 hours. The degree of discolorface of the test cup, an increase in friction and wear, or ation of the copper strip is obtained from a comparison unusual noise and vibration. Comparative results of luchart. A rating of la indicates slight discoloration and bricants containing additives of the present invention, consequently slight corrosivity of the additive towards other additives and the baseoil in the Timken test are copper. A test rating of lb, 2a, 212, etc. is less satisfacgiven in Table l. 1 I 1 tory. 1

It is critically important for the purposes of the pres- I The results obtained in testing dialkyl phosphonateent invention that the final lubricating composition l5 containing compositions .and comparing them with pass the 60-pound Timken test without excessive wear, other compositions containing phosphorous and sulfur in order to meet the requirements of the US. steel inhave been summarized in Table I.

TABLE I Analysis- Additive 4-Ball Falex Cu Timken Com onents .4 S I: P Cone... Wtfi; Wear. mm EP lbs. Strip EP lbs.

Base ()il (1.76-0.75 900-950 l'l 5-H) Bis-h \'tlrosypuIyprtipylencphenyl disulliile Z (1.36

Lntleuyl tnllutu 1.4 S 9.4 Z (L28 1331! l)otlec \l-tridec \'l tullute 1.4 S 7.3 Z (1.38 1350 Dutlcc l-tritlcc fl lilll'illC 1.4 Smith I i N} (L37 4 (1.37 lb Dudecyl-iridecxl tnllute I." S 0.01 I l: (1.12 4.3 (L47 4e 55 Dudee l-tritlecyl lullnlc 1.4 S/(Llf' (BU()). .PH() s4 0.97 4 0.47 2280 4:1 (in Number of moles ul' reactants per mule ol' ester 'Nt-uirnl oil 1\()) or |lUl\ lk'2l\lL'\l gear ml [(iO) dustry and other industrial users of extreme pressure The base oil is a paraffinic base neutral oil of viscosgear oils. For somewhat molder conditions oils carrying ity about 480 SUS at 100F, or a non-leaded gear oil 40-55 lb in the Timken test are satisfactory. It has been consisting of bright stocks and neutral oils with viscosfound that the P18 ratio, the total percent S and the ity about 1500 SSU at 100F. A dibutyl phosphonate ester structure itself are critical factors in meeting composition at a moderate level of sulfurization is seen those requirements. Additionally, if the formulation is to be u erior in Falex extreme pressure test and Timto be used with copper or copper alloy metals, then the ken extreme pressure test to all other extreme pressure perce t act e u u as measured. for P in additives tested. A particular advantage to the use of ASTM D l662-66T, should not rise above 10 percent. dialkyl phosphonate is the achievement of a 60 pound In the Four-Ball test a Steel hall t g at 1,300 pm Timken test at moderate levels of sulfur and phosphounder a load of 20 kg. is held against three stationary rous in the composition. This result is quite surprising steel balls in the form Of 21 cradle. The lubricating flUlCl in iew of the poorer results obtained from the ethyl "i. is brought to 75C and rotation occurs for a perlOCl 0f ester of phosphorous acid at similar concentrations. In 1 hour. after which the diameter 0f Scars on the rotat- 5o fact, esters treated with sulfur and dibutyl phosphonate ing ball is measured. In the Four-Ball test the load cardi l a surprising superiority in extreme pressure rying property of the lubricating fluid is measured as properties t th d ith th lLk h the ability of a lubricant to prevent wear at applied h lf i i agent P2S5 loads. Four-Ball test data for lubricating fluids containing g o p qo and other d i i are presented i The given examples illustrate specific syntheses of Table l, the preferred embodiments of this invention. They are Extreme pressure properties are l measured b intended to be illustrative rather than exhaustive. means of the Falex Machine Test. In the Falex test. stawhile the test results p y illustrate the superlomy of tionary Vee-blocks are pressed on either side of a rotatthe reflctlon Products of the P mvenflon as lubn' ing Steel h f by a nutcracker arrangement f lever eating oil and grease additives, other reaction products arms. Test specimens are immersed in a tank of test luformed m th pecified reagents 0f the present inbricant which has an unknown temperature. Loading is VehllOn would 21150 Perform as Superior extreme P increased until seizure occurs. The failure point is indir n arm-w r di i H ever. it i n possible cated by shearing of the pin holding the vertical shaft to attempt a comprehensive catalog of such reactants and the load at failure in pounds is taken as a quantita- .65 or to describe the invention in terms of specific chemical names of such reactants and reaction products without producing a voluminous disclosure. One skilled in the art could. by following the teaching of the invention herein described select the proper reactants and reaction conditions to provide a useful composition for his purpose. While the character of this invention has been described in detail with several examples. this has been done by way of illustration rather than limitation. It will be apparent to those skilled in the art that numerous modifications and variations of the illustrative examples can be made in the practice of the invention within the scope of the following claims.

What is claimed is:

l. The composition of matter prepared by reacting (1) an unsaturated ester formed by the reaction of a C,C alkanol or alkenyl with a C C- fatty acid, (2) sulfur, and (3) a C C dialkylphosphonate wherein the molar ratio of the reactants is about l:l-2:(). 1-0.5 and the reaction temperature is about l5()l C and reacted for a period of about 22() hours.

2. The composition of matter of claim I in which the unsaturated ester is an alkyl tallate.

3. The composition of matter according to claim 2 in which the alkyl tallate is the ester of derosinified tall oil and a C -C alcohol.

4. The composition of matter according to claim 3 in which the derosinified tall oil is a mixture of oleic and linoleic acids.

5. The composition of matter according to claim 1 in which the dialkyl phosphonate is dibutyl phosphonate, (C H O) PbO. 

1. THE COMPOSITION OF MATTER PRAPARED BY REACTING (1) AN UNSATURATED ESTER FORMED BY THE REACTION OF A C1-C25 ALKANON OR ALKENYL WITH A C10-C25 FATTY ACID, (2) SULFUR, AND (3) A C2-C18 DIALKYLPHOSPHONATE WHEREEIN THE MOLAR RATIO OF THE REACTANTS IS ABOUT 1:1-2:0.1-0.5 AND THE REACTION TEMPERATURE IS ABOUT 150*-180*C AND REACTED FOR A PERIOD OF ABOUT 2-20 HOURS.
 2. The composition of matter of claim 1 in which the unsaturated ester is an alkyl tallate.
 3. The composition of matter according to claim 2 in which the alkyl tallate is the ester of derosinified tall oil and a C1-C25 alcohol.
 4. The composition of matter according to claim 3 in which the derosinified tall oil is a mixture of oleic and linoleic acids.
 5. The composition of matter according to claim 1 in which the dialkyl phosphonate is dibutyl phosphonate, (C4H9O)2PbO. 